JP4311837B2 - Power supply circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply circuit mounted on a portable information terminal device or the like, and more particularly to a power supply circuit having a backup function when supply of main power is stopped.
[0002]
[Prior art]
In recent years, notebook personal computers equipped with semiconductor memories, word processors, and portable information terminal devices (hereinafter referred to as portable terminals) such as electronic notebooks (PDAs) have become widespread, and are particularly remarkable for technological innovations in miniaturization and weight reduction. There is something. These portable terminals are driven by loading a battery or a rechargeable battery as a main power source (main battery) when power is not supplied through a cable.
[0003]
At the time of replacement of the battery or the like, a backup power source (backup battery) is mounted in order to retain the information content stored in the semiconductor memory such as RAM.
[0004]
[Problems to be solved by the invention]
In these portable terminals, it is difficult to cover all the drive circuits with one power supply voltage due to the drive characteristics of the constituent parts, and at least two different voltages are required, and two power supply units are provided.
[0005]
Therefore, in order to back up the main power source, as shown in FIG. 3B, when two power supply units 11 and 12 are provided for the main battery E1, the power source voltage is backed up. Backup batteries E3 and E4 were provided. However, the battery occupies a considerable proportion in terms of the total weight of the mobile terminal, and it is necessary to always install two extra batteries in order to improve portability, that is, to reduce the size and weight. It becomes an obstacle.
[0006]
Therefore, the power supply voltage is designed to be covered by one backup battery E2 as shown in FIG. In this configuration, a power supply unit (3.3V system) 11 and a power supply unit (2.5V system) 12 are connected in series, and a backup battery E2 is provided therebetween. The backup battery E2 is usually mounted with a backup battery that supplies power in accordance with the high voltage side (here, 3.3V system), and is used after being stepped down by the power supply unit 12.
[0007]
In general, when a circuit element is driven, a part of the supplied energy is converted into heat or the like and consumed, so that energy less than the input energy is output. Therefore, even in a power supply unit composed of a large number of circuit elements, a certain degree of output degradation occurs due to efficiency.
[0008]
In order to cover two power supply voltages with such a single backup battery, when two power supply units are connected in series and driven by a normal main power supply, the second-stage power supply unit 12 Then, due to the inefficiency, the main power source is always wasted. Therefore, in a portable terminal using a battery or the like as a main power source, the operation time is shortened, and when the size and weight are reduced, the operation time is further shortened.
[0009]
For this reason, if a smaller backup battery capacity is selected along with a reduction in size and weight, the backup battery will not be supplied temporarily unless the main power supply is loaded immediately after the backup battery is switched to power supply. This leads to a problem that important information held is lost.
[0010]
Therefore, the present invention provides a power supply circuit having a function of backing up two power supply units connected in parallel by switching the power supply of one backup battery when the power supply by the main power supply is stopped. The purpose is to do.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a main power source, a first power supply unit that is connected to the main power source and supplies power to a first voltage driving circuit that is driven by a first voltage, and the main power source. A second power supply unit that is connected in parallel to the first power supply unit and supplies power to a second voltage driving circuit that is driven by a second voltage different from the first voltage; A backup power source provided at a subsequent stage of the one power supply unit and supplying power to the first voltage driving circuit and the second voltage driving circuit when the main power source is turned off; A power supply circuit comprising a backup power supply control unit for controlling power supply to the first and second voltage driving circuits is provided.
[0012]
In this power supply circuit, the backup power supply control unit supplies power to the second power supply unit according to an output from the off-state detection unit that detects the off-state of the main power supply and the off-state detection unit. Switch means for switching to a backup power source. The backup power supply control unit controls the power supply from the backup power supply to the second power supply unit until the end processing of the central processing unit as the second drive circuit is completed.
[0013]
In the power supply circuit configured as described above, when the off-state detection unit detects the supply stop of the main power supply or the drop in the supply voltage, the power supply to the second voltage drive circuit is used as the power supply from the backup power supply to the switch means. While instructing to switch, the controller that controls the operation of the first and second voltage drive circuits is instructed to end the operation of the first and second voltage drive circuits, and the first and second voltage drive circuits can be restarted. After finishing the operation, the operation of the second power supply unit is stopped.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 shows an example of a circuit configuration of a power supply circuit according to an embodiment of the present invention. The power supply circuit according to this embodiment is suitable for a mobile terminal.
[0016]
The power supply circuit includes a first power supply unit 2 that outputs a first power supply (for example, 3.3V) and a second power supply (for example, 3.3V) by supplying power from a main power supply 1 including a battery and a rechargeable battery. , 2.5V), the first power supply unit 2 supplies the first power to the first voltage driving circuit 6 (3.3 V system), The second power supply unit 3 is configured to supply the second power to the second voltage drive circuit 7 (2.5V system), and a backup battery 5 is provided on the output side of the first power supply unit 2. ing.
[0017]
The first voltage driving circuit 6 and the second voltage driving circuit 7 are controlled by a central processing unit (CPU) 8. The CPU 8 operates at a low voltage inside because of low power consumption operation, but the interface portion with the outside operates at the same voltage as a general peripheral IC, so two different power supply voltages are supplied. Is used inside the CPU 8 and the other is supplied to the interface with the outside of the CPU 8 and to the peripheral IC.
[0018]
In the present embodiment, it is assumed that the first voltage drive circuit 6 has a volatile memory 9 that always needs to be supplied with a very small amount of power in order to retain the stored contents.
[0019]
In the second power supply unit 3, the terminal 4a is connected to the main power supply 1, the terminal 4b is connected to the output side of the first power supply unit 2, and the switching terminal 4c is connected to the input side of the second power supply unit. One of the selected power supplies is supplied via the switch circuit 4 that performs the above operation. The operation of the second power supply unit 3 is controlled by a control signal from the CPU 8.
[0020]
Further, this power supply circuit is provided with a voltage detection circuit 10 for detecting the voltage value of the power supply supplied by the main power supply 1. When a low voltage of the main power supply 1 is detected, the detection signal is sent to the switch circuit 4 and Simultaneously output to the CPU 8. The switch circuit 4 uses this detection signal as a switch switching signal.
[0021]
In the normal driving state of the power supply circuit configured as described above, the switch circuit 4 is connected to the terminal 4a side. Accordingly, power is supplied from the main power supply 1 to the first power supply unit 2 and the second power supply unit 3, and the first power supply is supplied to the first voltage drive circuit 6 and the second power supply is supplied to the second voltage drive circuit 7, respectively. Supplied.
[0022]
Next, with reference to the flowchart shown in FIG. 2A, a stop routine will be described when the main power supply 1 is removed or the supply voltage is lowered. In this power supply circuit, since the same processing is performed when the main power supply 1 is removed and when the supply voltage is lowered, the case where the main power supply 1 is removed will be described here.
[0023]
First, when the main power supply 1 is removed, the power supply to the first power supply unit 2 and the second power supply unit 3 is stopped, and the drive is stopped together (step S1). However, the power supply to the first voltage drive circuit 6 is switched to the backup battery 5 without stopping the power supply.
[0024]
At this time, the voltage detection circuit 4 detects a voltage drop (step S2), and simultaneously outputs a low voltage detection signal to the switch circuit 4 and the CPU 8 (step S3).
[0025]
Upon receiving this detection signal, the switch circuit 4 switches from the terminal 4a to the terminal 4b, and power supply from the backup battery 5 to the second power supply unit 3 is started. The CPU 8 that receives the detection signal almost simultaneously with this starts a preprogrammed end process (step S4).
[0026]
This termination process stops the driving of each circuit element except for the volatile memory 9 that always needs to supply a small amount of power in order to maintain the stored contents in the first voltage driving circuit 6 and the second voltage driving circuit 7, Transition to a low battery consumption state.
[0027]
Thereafter, the CPU 8 stops the driving of the second power supply unit 3, and the CPU 8 itself stops supplying power to a part other than that necessary for restarting (step S <b> 5), and the series of processing ends.
[0028]
Thus, by switching the switch circuit 4 from the terminal 4a to the terminal 4b, the power supply circuit of this embodiment has a circuit configuration in which two power supply circuits as shown in FIG. Thus, two different voltages can be supplied.
[0029]
Next, with reference to the flowchart shown in FIG. 2B, a routine in which a new main power supply (battery) is loaded in the power supply circuit in which the power supply of the main power supply 1 is stopped will be described.
[0030]
First, when a new battery or the like is loaded in the power supply circuit as the main power supply 1, power supply to the first power supply unit 2 is started (step S11). At this time,
At this time, the voltage detection circuit 4 detects the return of the normal supply voltage (step S12), and simultaneously outputs a normal supply voltage detection signal to the switch circuit 4 and the CPU 8 (step S13).
[0031]
Upon receiving this detection signal, the switch circuit 4 switches from the terminal 4b to the terminal 4a, and power supply from the main power supply 1 is started to the second power supply unit 3. When power supply from the main power supply 1 is started, the first power supply unit 2 outputs the first power supply and switches from the power supply by the backup battery 5. Upon receiving the detection signal almost simultaneously with this, the CPU 8 performs a process such as initialization upon restarting, and returns to a normal operation state (step S14).
[0032]
As described above, since the power supply circuit of the present invention has a configuration in which two power supply units are connected in parallel in normal operation, power is supplied from the main power supply. Compared with the conventional arrangement connected in series, a reduction in efficiency can be prevented.
[0033]
Further, since two power supply units can be backed up by one backup power source, it is not necessary to provide two backup power sources having different voltages as in the conventional configuration, and there is an effect of contributing to reduction in size and weight. .
[0034]
Also, when the main power supply stops or the supply voltage drops, the power to all peripheral circuits except the memory that needs to retain the contents is cut off, and the power supply to the CPU itself is stopped. Since the termination process is performed, the power consumption is minimized after switching to the power supply by the backup power supply, and a long-time backup can be realized.
[0035]
Although the above embodiments have been described, the present invention includes the following inventions.
[0036]
(1) a main power supply for supplying power for normal use;
A first power supply unit that is connected to the main power supply and supplies the first power to a first voltage driving circuit that is driven by a first voltage;
A second power source connected to the main power source in parallel with the first power supply unit and supplying the second power source to a second voltage driving circuit driven by a second voltage lower than the first voltage. A power supply unit;
A backup power supply provided on the output side of the first power supply unit and supplying power to the first voltage drive circuit and the second voltage drive circuit when the main power supply is stopped;
A switching unit having a switching terminal connected to the input side of the second power supply unit, switching between the first terminal connected to the main power source and the second terminal connected to the output side of the first power supply unit When,
A voltage detection unit for detecting a decrease in supply voltage from the main power supply or a power supply stop, and
When the voltage detection unit detects the supply stop of the main power supply, the switching unit is instructed to switch the power supply to the second voltage driving circuit to the power supply from the backup power supply, and the first and second voltages After the operation of the first and second voltage drive circuits is suggested to the control unit that controls the operation of the drive circuit, and the first and second voltage drive circuits are finished to be restartable, the second power supply unit The power supply circuit is characterized in that the operation of the power supply is stopped and the backup power supply is brought into a low consumption state.
[0037]
(2) The first power supply unit supplies a current of voltage 3.3V to various circuits, and the second power supply unit supplies a current of voltage 2.5V to the central processing unit. The power supply circuit according to item (1), characterized in that:
[0038]
【The invention's effect】
As described in detail above, according to the present invention, when the power supply by the main power supply is stopped, the function of backing up two power supply units connected in parallel by switching the power supply of one backup battery and supplying it is provided. Can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a circuit configuration example of a power supply circuit according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining an operation of the power supply circuit according to the embodiment.
FIG. 3 is a diagram conceptually showing a configuration of a conventional power supply circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Main power supply 2 ... 1st power supply part 3 ... 2nd power supply part 4 ... Switch circuit 4a, 4b ... Terminal 4c ... Switching terminal 5 ... Backup battery 6 ... 1st voltage drive circuit 7 ... 2nd voltage drive circuit 8 ... Central processing unit (CPU)
9 ... Memory 10 ... Voltage detection circuit

Claims (4)

A main power supply,
A first power supply unit that is connected to the main power supply and supplies power to a first voltage driving circuit driven by a first voltage;
A second power supply unit connected to the main power supply in parallel with the first power supply unit and configured to supply power to a second voltage driving circuit driven by a second voltage different from the first voltage;
A backup power supply provided at a subsequent stage of the first power supply unit and supplying power to the first voltage drive circuit and the second voltage drive circuit when the main power supply is turned off;
A backup power supply controller for controlling power supply from the backup power supply to the first and second drive circuits;
A power supply circuit comprising: The backup power supply control unit includes an off state detection unit that detects an off state of the main power source,
Switch means for switching the power supply to the second power supply unit to a backup power supply according to the output from the off-state detection unit;
The power supply circuit according to claim 1, further comprising: The backup power supply control unit controls the power supply from the backup power supply to the second power supply unit until the end processing of the central processing unit as the second drive circuit is completed. The power supply circuit according to claim 2. A first power supply unit that generates a first voltage by power supply from a main power supply;
A second power supply unit, wherein the first power supply unit and the input side are connected in parallel, and a second voltage is generated by power supply from a main power supply;
A backup power source disposed on the output side of the first power supply unit;
A backup power supply control unit that switches the input side of the second power supply unit from the main power supply to the backup power supply when a stop of power supply of the main power supply or a power supply voltage drop is detected;
A power supply circuit comprising:

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